Al-Riʾāl (الرِّئَال)

Authors: Khalid Al-Ajaji

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Al-Riʾāl and the neighbouring Arabic asterisms described in the Anwāʾ sources. (CC BY Khalid Al-Ajaji 2026).

Al-Riʾāl (الرِّئَال, “the ostrich chicks”) is a traditional Arabic asterism identified with four groups of three stars stepping north-eastward across southern Aquarius and into Cetus. The groups lie between Fomalhaut (α Piscis Austrini) and Diphda (β Ceti), identified in the tradition as the two male ostriches, al-Ẓalīmān.

Etymology

The Arabic word الرِّئَال is the plural of رَأْل, “a young ostrich” or “ostrich chick.” The name belongs to a dense cluster of desert-bird imagery in this region of the traditional Arabic sky: al-Ẓalīmān (the two male ostriches), al-Naʿāmāt (the ostriches), al-Udḥiyy (the ostrich nest), al-Qaṭā (the sandgrouse), al-Makākī (larks), al-Yamāmatān (doves), and al-Ṣuradān (shrikes).

Sources

Ibn Qutayba

Ibn Qutayba (d. 276 AH / 889 CE) describes the two bright al-Ẓalīmān and places al-Riʾāl between them as stars arranged in graded steps. He then places al-Naʿāmāt and al-Udḥiyy after al-Riʾāl:

ثم الظَّلِيمَانِ فوق ذلك، وهما كوكبان نيران [بينهما] في رأي العين إذا استويا في السماء قدر مائة ذراع، وبينهما «الرِّئَالُ»، كواكب مدرجة، وبعد الرِّئَالِ «النَّعَامَاتُ»، وهي خمسة كواكب على تربيع النَّعْشِ. وعلى أثرها «الأُدْحِيُّ»، وهي كواكب مستديرة على قدر دارة القمر.

English

Then above that are the two male ostriches: two bright stars, [between which], to the eye when they are level in the sky, is a distance of one hundred cubits. Between them are al-Riʾāl, stars arranged in graded steps. After al-Riʾāl are al-Naʿāmāt, five stars in the pattern of the Bier; and following them is al-Udḥiyy, stars arranged in a circle the size of the Moon’s orbit.

Al-Marzūqī

Al-Marzūqī (d. 421 AH / 1030 CE) transmits the same essential description in a different order within the passage:

وثم الظَّلِيمَانِ فوق ذلك، وهما كوكبان نيّران، بينهما في رأي العين إذا استويا في السّماء قدر مئة ذراع، وبينهما الرِّئَالُ.

English

And then above that are the two male ostriches, two bright stars. Between them, to the eye when they are level in the sky, is a distance of one hundred cubits; and between them are al-Riʾāl.

Identification

Al-Riʾāl is identified with four ordered triplets extending from southern Aquarius into Cetus. Visual magnitudes range from V = 3.66 for 88 Aquarii to approximately V = 5.2.

Proposed groups of al-Riʾāl

Group	Stars
1	86 Aquarii, 89 Aquarii, 88 Aquarii
2	101 Aquarii, 99 Aquarii, 98 Aquarii
3	104 Aquarii, 106 Aquarii, 108 Aquarii
4	HIP 301, HIP 983, HIP 1170

Astronomical correspondence

The proposed identification accounts for the phrase كواكب مدرجة (“stars arranged in graded steps”). Rather than an undifferentiated scatter, the configuration forms ordered clusters of three stars that progress north-eastward.

On a dhirāʿ calibrated from the pairs of the Suʿūd (mean approximately 2.03°), each brood is about one dhirāʿ across and the intervening gaps are about two and a half dhirāʿ. The triplet structure also corresponds closely to the name: ostrich chicks occur in broods, with four such broods placed between the two adult birds.

Al-Ẓalīmān

The two Ẓalīmān (“male ostriches”) that flank al-Riʾāl are identified with Fomalhaut (α Piscis Austrini; V = 1.16) and Diphda (β Ceti; V = 2.04). The identification satisfies the principal features of the notice:

• The two stars are the brightest stars in the relevant quadrant, matching كوكبان نيّران (“two bright stars”).
• Fomalhaut lies at RA 22.961^h and Diphda at RA 0.726^h. The four proposed broods lie in sequence between them, at approximately RA 23.14^h, 23.45^h, 23.76^h, and 0.20^h.
• The two stars are separated by 26.79°. The broods lie about 6° north of the great circle joining them, consistent with “between” in the positional sense required by a brood rather than strict collinearity.

The al-Ẓalīmān and al-Riʾāl also support a brightness sequence in the terminology of the Anwāʾ tradition:

Brightness vocabulary in the proposed identifications

Arabic description	Referent	Measured visual magnitude
نيّران	Al-Ẓalīmān	V = 1.16–2.04
بيض	Al-ʿUdhra	V = 1.50–3.47
زهر	Al-Aʿlām	V = 3.03–3.75
غير نيّرة	Al-Qaṭā	V = 4.21–5.01

The hundred dhirāʿ

The phrase قدر مائة ذراع (“about one hundred cubits”) is preserved consistently and should not be emended merely to produce a plausible angular separation. The recorded readings are:

Witness	Reading
Ibn Qutayba manuscript	قدرُ ماية دراع
Ibn ʿĀṣim al-Ṯaqafī manuscript	قدر ماىه ذراع
Al-Marzūqī, both printed editions	قدر مائة ذراع

The rasm م-ا-ٮ-ه admits مائة as the relevant numeral, and the singular genitive ذراع is the grammatical construction governed by one hundred. The number is also written in words in both manuscripts, rather than represented by a numerical sign.

For small distances, the dhirāʿ functions as a stable angular unit of approximately two degrees. Six securely identified pairs in Ibn Qutayba yield a mean of about 2.02° per dhirāʿ, including examples expressed as one, three, and five dhirāʿ. Extrapolating that unit makes one hundred dhirāʿ approximately 202.4°, which cannot be an angular separation between the two stars.

The phrase is therefore best understood as a conventional large or round quantity rather than a literal angular measurement. In the same textual milieu, quantities such as twenty and one hundred dhirāʿ appear to mark “a considerable distance” and “a very great distance,” whereas smaller numbers represent distances laid off more literally in the sky.

Calibrating the dhirāʿ from securely identified pairs

Asterism	Stars	Stated distance	Measured separation	Implied one dhirāʿ
Saʿd Bulaʿ	ε–μ Aquarii	One dhirāʿ	1.35°	1.35°
Saʿd Nāshira	γ–δ Capricorni	One dhirāʿ	1.75°	1.75°
Saʿd al-Dhābiḥ	α²–β Capricorni	One dhirāʿ	2.35°	2.35°
Saʿd al-Suʿūd	β–ξ Aquarii	One dhirāʿ	2.69°	2.69°
Al-Ḥurrān / al-Dhiʾbān	η–ζ Draconis	Three dhirāʿ	6.50°	2.17°
Al-Zubānā	α²–β Librae	Five dhirāʿ	9.21°	1.84°

Relation to neighbouring asterisms

Al-Riʾāl forms the eastern half of the southern boundary of Al-ʿĀna. Al-Qaṭā occupies the western half, extending from approximately RA 21.0^h to 22.93^h at declination −31° to −33°. East of δ Piscis Austrini, al-Qaṭā ends and al-Riʾāl begins, running from approximately RA 23.1^h to 0.25^h at declinations about −17° to −24°.

The stars of al-Riʾāl are not part of al-ʿĀna: they lie approximately two to five degrees south of its boundary. In the strip from Fomalhaut to Diphda, there are no stars brighter than V = 5.5. α Sculptoris (V = 4.30) and δ Sculptoris (V = 4.57) are the nearest brighter candidates, but lie four to five degrees south of that line in an otherwise unassigned area of Sculptor.

Textual transmission

Al-Marzūqī transmits the relevant passage through Abū Ḥanīfa al-Dīnawarī in a continuous chain of attribution, while Ibn ʿĀṣim al-Ṯaqafī quotes both Ibn Qutayba and Abū Ḥanīfa. Abū Ḥanīfa (d. 282 AH) was a contemporary of Ibn Qutayba (d. 276 AH), and therefore cannot be the direct archetype of Ibn Qutayba’s text. Their close agreement instead points to an older shared authority, plausibly within the generation represented elsewhere in al-Marzūqī’s material by Ibn al-Aʿrābī (d. 231 AH) and Abū Zayd al-Kilābī.